The present invention relates to a III-Nitride power semiconductor device and a method for fabrication thereof.
III-nitride power semiconductor devices are commercially desirable due to their high band gap and high current carrying capabilities.
A typical III-nitride power semiconductor device, for example, a III-nitride high electron mobility transistor (HEMT), includes a III-nitride heterojunction which serves as a current conduction channel between two power electrodes. Specifically, a HEMT according to the prior art includes a first III-nitride semiconductor body, which may be composed of, for example, undoped GaN, and a second III-Nitride semiconductor body, which may be composed of, for example, N-type AlGaN, disposed over the first semiconductor body. The first semiconductor body may be formed over a transition body composed, for example, of AlN, which is itself formed over a substrate.
As is well known, the heterojunction of the first semiconductor body and the second semiconductor body results in the formation of a carrier-rich conductive region usually referred to as a two dimensional electron gas or 2DEG. Current may be conducted between a first ohmic contact (which is ohmically coupled to second semiconductor body), and a second ohmic contact (which is also ohmically coupled to second semiconductor body) through the 2DEG.
A conventional HEMT, is a normally ON device. In many applications it is desirable to turn the device off or have a normally OFF device. Thus, a gate electrode may be disposed between the first ohmic contact and the second ohmic contact. The application of an appropriate voltage to the gate electrode causes the interruption of the 2DEG thereby turning the device OFF. Thus, to operate a conventional HEMT as a normally OFF device requires the continued application of a voltage to the gate electrode, which is not desirable as it consumes more energy, and may also require a more complicated drive circuitry compared to a normally OFF device.